**4.1 Characterization of the silica templates**

TEM images obtained from the silica samples taken at 30, 60, 90, and 120 min after adding the TEOS are presented in **Figure 7**. When comparing the images, no significant variation in the size of the silica particles is noticeable.

To corroborate that the silica particles do not change substantially when the reaction time is over 30 min, the images were studied with the software Image J®, and the diameter distribution of the particles was analyzed. Over 1000 particles from the different samples were measured to obtain the histograms presented in **Figure 8** where samples A, B, C, and D correspond to 30, 60, 90, and 120 min of reaction time, respectively. They illustrate that the diameter distribution of the silica spheres throughout the synthesis oscillates around the 190 ± 5 nm on all the samples.

To have a better understanding of the information, **Table 1** contains useful statistic information from the samples.

**Figure 7.** *TEM images of silica particles at (a) 30, (b) 60, (c) 90, and (d) 120 min after adding TEOS.*

**Figure 8.** *Histograms illustrating the diameter distribution of the silica particles throughout their synthesis.*


#### **Table 1.**

*Statistic information obtained by measuring the diameters of silica particles from the different samples.*

The mean, standard deviation, and mode obtained after analyzing the samples show that, in general, the silica templates keep their size and shape after 30 min of synthesis. Therefore, the objective of synthesizing silica particles with diameters of 190 ± 5 nm was achieved within 30 min of reaction time. More than 30 min of synthesis does not result in any relevant change in the sample. For this reason, the total process time can be reduced from 2 h to 30 min, shortening the reaction time by 1 h and 30 min when compared with similar published works where the synthesis time is at least 2 h [10, 17, 27, 28].

#### **4.2 Characterization of the functionalized silica templates**

The functionalization of the silica with a primary amine group (–NH2) was accomplished by the use of APTES which changed the superficial charge of the

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**Figure 10.**

*TEM images of GNPs.*

**Figure 9.**

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy*

*FTIR spectrum of silica particles and silica particles functionalized with APTES.*

silica providing an electrostatic link for the GNPs to attach [29]. This superficial modification was verified by the FTIR spectrum shown in **Figure 9** where the vibra-

which correspond

tions of primary amines are found between 3550 and 3330 cm<sup>−</sup><sup>1</sup>

to the vibrations of a primary amine group [30].

*DOI: http://dx.doi.org/10.5772/intechopen.82495*

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy DOI: http://dx.doi.org/10.5772/intechopen.82495*

*Current Topics in Biochemical Engineering*

The mean, standard deviation, and mode obtained after analyzing the samples show that, in general, the silica templates keep their size and shape after 30 min of synthesis. Therefore, the objective of synthesizing silica particles with diameters of 190 ± 5 nm was achieved within 30 min of reaction time. More than 30 min of synthesis does not result in any relevant change in the sample. For this reason, the total process time can be reduced from 2 h to 30 min, shortening the reaction time by 1 h and 30 min when compared with similar published works where the synthesis time

*Statistic information obtained by measuring the diameters of silica particles from the different samples.*

**Count Mean Std dev. Mode**

*Histograms illustrating the diameter distribution of the silica particles throughout their synthesis.*

Sample A 250 187 25 197 (79) Sample B 287 162 18 162 (80) Sample C 265 196 16 201 (92) Sample D 250 197 13 198 (105)

The functionalization of the silica with a primary amine group (–NH2) was accomplished by the use of APTES which changed the superficial charge of the

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**Figure 8.**

**Table 1.**

is at least 2 h [10, 17, 27, 28].

**4.2 Characterization of the functionalized silica templates**

**Figure 9.** *FTIR spectrum of silica particles and silica particles functionalized with APTES.*

**Figure 10.** *TEM images of GNPs.*

silica providing an electrostatic link for the GNPs to attach [29]. This superficial modification was verified by the FTIR spectrum shown in **Figure 9** where the vibrations of primary amines are found between 3550 and 3330 cm<sup>−</sup><sup>1</sup> which correspond to the vibrations of a primary amine group [30].

#### **Figure 11.**

*SEM images illustrating the seeding process with (a) 30 min of resting time and (b) 2 h of resting time.*

#### **Figure 12.** *TEM image of a gold decorated silica particle.*

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**Figure 14.**

*and (e) gold nanoshells.*

*A Simple Way to Produce Gold Nanoshells for Cancer Therapy*

diameter of 7 ± 3 nm and spherical shape overall.

**4.4 Characterization of the gold nanoshells**

which causes the increase in temperature.

**4.5 The UV-Vis spectrum**

**4.3 Characterization of the gold nanoparticles and seeded silica**

display approximately the same number of nucleus per silica particle.

The GNPs were analyzed under a TEM. **Figure 10** illustrates the GNPs with a

The seeding process was followed with 2 h of still time as well as with 30 min of still time. The first and second samples were observed under the microscope. The samples were taken with the purpose of observing the development of the seeds. **Figure 11a** presents an SEM image of seeded silica with 30 min of resting time, while **Figure 11b** presents an SEM image of seeded silica with 2 h of resting time. The images show that 30 min is enough time to create the seeds because both images

Even though a complete shell was not formed, the seeds are ready to grow the gold shell on the next step. A TEM image of a seeded silica particle is presented in **Figure 12**. This image corroborates the seeding process as well as the silica functionalization.

**Figure 13a** and **b** presents SEM and TEM images of the synthesized GNS, respectably. They illustrate that the silica particles are almost surrounded by gold. The higher density of gold, the separation of the GNPs [31], and the dielectric properties of the silica [3] contribute to the absorption of the NIR wavelength,

**Figure 14** presents the UV-Vis spectrum of the particles through the process. Silica particles, as well as functionalized silica particles, do not show significant

*UV-Vis spectrum of (a) silica, (b) functionalized silica, (c) gold nanoparticles, (d) gold seeded silica,* 

*DOI: http://dx.doi.org/10.5772/intechopen.82495*

**Figure 13.** *(a) SEM and (b) TEM images of GNS.*

*Current Topics in Biochemical Engineering*

*SEM images illustrating the seeding process with (a) 30 min of resting time and (b) 2 h of resting time.*

**Figure 11.**

**Figure 12.**

*TEM image of a gold decorated silica particle.*

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**Figure 13.**

*(a) SEM and (b) TEM images of GNS.*
